Optical transmission systems, including optical fiber communication systems, have become an attractive alternative for carrying voice and data at high speeds. While the performance of optical communication systems continues to improve, there is increasing pressure on each segment of the optical communication industry to reduce costs associated with building and maintaining an optical network.
One useful technology for improving performance and reducing the overall cost of the optical communication system is through the use of wavelength division multiplexing (WDM). As is well known, WDM pertains to the transmission of multiple signals (in this case optical signals) at different wavelengths down a single waveguide (e.g., optical fiber) with a channel being assigned to each wavelength, and each channel having a particular bandwidth. The nominal wavelength of a given channel is often referred to as the channel center wavelength.
For purposes of illustration, according to one International Telecommunications Union (ITU) grid a wavelength band from 1530 nm to 1565 nm is divided up into a plurality of wavelength channels, each of which have a prescribed center wavelength and a prescribed channel bandwidth; and the spacing between the channels is prescribed by the ITU grid.
For example, one ITU channel grid has a channel spacing requirement of 100 GHz (in this case the channel spacing is referred to as frequency spacing), which corresponds to channel center wavelength spacing of 0.8 nm. With 100 GHz channels spacing, channel “n” would have a center frequency 100 GHz less than channel “n+1” (or channel n would have a center wavelength 0.8 nm greater than channel n+1).
In WDM systems all of the channels are combined (multiplexed) at one end of the system, and separated (demultiplexed) at the other end for further use. The separation of individual wavelength channels may be carried out using optical filters. Currently, most multiplexing/demultiplexing schemes are based on fixed filters. However, there is a need in optical networks to provide flexibility that is not afforded by conventional fixed filter designs.
In addition to WDM systems, optical filters are useful in certain laser and amplifier applications. The lasers used in optical communication systems may be tunable. Moreover, erbium-doped fiber amplifiers (EDFA's) have been deployed widely in optical communication and sensor applications. Optical filters may be used to suppress broadband amplified spontaneous emission (ASE) around the signal from EDFA's and tunable lasers.
Accordingly, optical filter arrays serve a useful purpose in a variety of applications. What is needed is an optical filter array that overcomes the shortcomings of conventional optical filter arrays.